The present invention relates to a magnetic tape cassette, and particularly to a magnetic tape cassette of a type in which a magnetic tape is pulled out from the front of the cassette for recording and playback.
High-density recording has been recently been made possible using magnetic tape cassettes. Typical of such magnetic tape cassettes are VHS- and Beta-type cassettes for home use and M-type cassettes for commercial use. Although magnetic tape cassettes of such types employ different recording formats and have slight differences in their construction, in each case a magnetic tape is pulled out from a front opening in the cassette for recording and playback. The magnetic tape cassette is provided with a turnable guard panel which closes the front opening when the cassette is not in use and exposes the opening for recording the playback of the cassette.
When the magnetic tape cassette is loaded in a video cassette recorder, the cassette is first horizontally inserted into the machine and then moved in the direction (downward in general) of thickness of the cassette so that the guard panel is moved to open the front opening. Then, a tape pull-out member is moved to the back (nonmagnetic side) of the magnetic tape to appropriately pull the tape out of the cassette through the opening.
In order to avoid mistaking one magnetic tape cassette type for another, different configuration of guide grooves are provided on the cases of the cassettes to prevent insertion of the wrong type of cassette into a particular recording/playback apparatus, which has an insertion guide which will receive only one type of cassette. The length and depth of the guide grooves must be set at prescribed values to ensure proper interaction of the guide grooves and the insertion guide. That is, the positions of the guide groove and the insertion guide at the central area of the bottom of each magnetic tape cassette are made slightly different for each type of cassette. However, since the positions of the guide groove and the insertion guide are only made slightly different among conventional cassettes and recording/playback apparatuses, the guide groove of a cassette smaller in size than the proper cassette for a particular recording/playback apparatus can sometimes be mistakenly inserted into the machine, causing jamming or possibly damage to the machine.
Much research and development has recently been conducted in order to enable recording and playback of even higher quality than before, and new magnetic tape cassettes have been proposed which are capable of recording and playback of higher densities than before. If such new magnetic tape cassettes are similar in form to conventional cassettes, the above-mentioned problems are likely to become more prominent.
Moreover, even the proper magnetic tape cassette for a particular machine can sometimes be inserted upside down. In order to prevent such mistaken insertion, the guard panel of the conventional cassette is provided with a notch at the top of the guard panel corresponding to the position of the guide of the cassette holder during upside down insertion. For example, when a conventional magnetic tape cassette as shown in FIG. 1 is inserted upside down into the cassette holder of a recording/playback apparatus, the cassette comes into contact with the insertion guide of the cassette holder at a notch 10a provided in the guard panel 5a of the cassette at the top of the central part of the panel to thus prevent mistaken insertion. However, if the guard panel 5a comes into strong contact with the insertion guide, the guard panel can be strongly flexed, causing it to be deformed plastically or damaged. In an extreme case, the guard panel 5a can pass over the insertion guide at the notch 10a so that the magnetic tape cassette is completely mistakenly inserted into the recording/playback apparatus.
Moreover, although the opening of most conventional magnetic tape cassettes is closed at the front (facing the magnetic film side of the magnetic tape in the cassette) and top of the cassette by the guard panel, a front opening provided in the bottom of the cassette to allow inserting of the tape pull-out member into the front opening remains open so that dust or the like is likely to enter the cassette through the front opening. Also, finger contact or the like with the magnetic tape can occur when the cassette is handled. This can result in increasing the occurrence of dropout caused by dust or the like and can result in deformation of the magnetic tape, causing a deterioration of the recording/playback properties thereof. Therefore, it is difficult to maintain the performance of a magnetic tape cassette for long periods of time.
In order to solve such problems, a guard panel having improved dustproofing characteristics and providing better protection in general has been desired. For example, it is desirable to employ a guard panel composed of inner and outer guard panels between which the magnetic tape is supported. Doing so, however, greatly complicates the structure of the magnetic tape cassette and makes it more likely that deformation or the like of the guard panel will occur upon mistaken insertion of the cassette.